INTRODUCTIONIn the early years of systematic entomology Johann Christian Fabricius (1745-1808) described an enormous number of insects, including several hundreds of Hymenoptera, from various parts of the world. His descriptions are generally short and incomplete, the classification of the species is often unsatisfactory, and the author himself frequently misidentified species which he had described in previous works.His work has thus raised a considerable number of problems, which in most cases can be solved only by a study of the typical specimens. Workers in some insect groups have realised this at an early date, and by a detailed study of the Fabrician collections they have made important contributions to our knowledge of many doubtful species. A good example is C. Stål's excellent work "Hemiptera Fabriciana", published in 1868 and 1869.The Hymenoptera, however, have received only relatively little attention, and even European monographers have generally neglected to clarify the position of the Fabrician species by the study of authentic material. A notable exception is A. G. Dahlbom, who identified, aided by Prof. Behn in Kiel, the types of several Sphecoidea and Pompilidae on behalf of his "Hymenoptera Europaea" (1843-5). In 1912 W. A. Schulz examined a number of doubtful species, and in later years certain types have been studied in connection with investigations made by Turner, Betrem, Richards, de Beaumont, Lieftinck, and others. Yet a considerable number of species has never been identified by competent specialists, including some species which have been a real or potential source of confusion and misunderstandings for over 150 years.